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Nanoparticle Drug Delivery System Developed at UB

Photonics.comAug 2003
BUFFALO, N.Y., August 4 -- Scientists at the University at Buffalo's (UB) Institute for Lasers, Photonics and Biophotonics, working with colleagues at the Roswell Park Cancer Institute, have developed a nonrelease nanoparticle drug delivery system for photodynamic cancer therapy.

Because the ceramic-based nanoparticle developed at the university never releases photosensitizing drugs into the bloodstream, it could overcome the main side effect associated with photodynamic cancer therapy (PDT): patients' strong sensitivity to light for four to six weeks after treatment, according to the UB researchers.

Their findings were published last month in the Journal of the American Chemical Society. A provisional patent has been filed.

PDT, which originated at Roswell Park Cancer Institute, is one of the most promising treatments for cancer, according to a UB press release; it's also being investigated as a treatment method for cardiovascular, dermatological and ophthalmic diseases.

PDT exploits the propensity of tumors to retain higher concentrations of photosensitive drugs than normal tissues. When exposed to laser light, these drugs generate toxic molecules that destroy the cancer cells.

"What happens after treatment is that the free drug diffuses throughout the body and accumulates in the patient's skin and eyes, making them very sensitive to light," said Indrajit Roy, PhD, lead author and a postdoctoral researcher at the Institute for Lasers, Photonics and Biophotonics.

"With the nanoparticle that we have developed, the hydrophobic photosensitizing drugs can be dispersed more readily, since they are encapsulated by a water-compatible shell," said Roy. "Once encapsulated, the drug remains inside the particle and is not released into the surrounding environment."

A key feature of the nanoparticle developed at UB, which measures about 35 nanotmeters, is the size of its pores, between just .5 and 1.0 nanometers. A nanometer is one-billionth of a meter. The pore size allows oxygen to diffuse freely back and forth. That's critical, because when laser light activates the photosensitizing drugs inside the nanoparticle, the drugs pass on the excess energy to molecular oxygen, converting it to singlet oxygen, which is highly toxic to cells. The singlet oxygen is what destroys the cancer cells.

The ceramic-based nanoparticle is a member of a new class of materials known as organically modified silica, or ORMOSIL, which are known for their extreme stability. These materials, Roy said, can be synthesized readily at ambient temperatures with the desired size, shape and porosity.